İsmail Bey Mosque is the focus of a small külliye built in the 1440s, when Kastamonu was still shaped by the Candarid dynasty. Its position near the old hillside quarter makes it a useful companion to the castle walk.
The complex is quieter than Nasrullah Mosque, and that helps. It gives Kastamonu's pre-Ottoman history a clear, visitable address rather than leaving it as a line in the guidebook.